The proposed investigation is designed to study the effect of aging on vitamin B-6 metabolism. Possible mechanisms for marginal vitamin B-6 status in the elderly will be investigated. These include changes in vitamin absorption, phosphorylation and urinary loss of the vitamin. The long term objective of this study is to determine whether vitamin B-6 requirement is altered with aging. Thirty-six healthy male volunteers will be selected, so that there are 12 subjects each in each of the 3 age groups 25-35, 45-55 and 65-75 years. A small oral dose of pyridoxine HC1 (4 mgs) will be administered to fasting subjects in the form of a multivitamin mineral supplement. Blood and urine samples will be obtained before and at 0.5, 1, 2, 3 and 4 hours after ingestion of the vitamin dose. The blood samples will be assayed for total plasma vitamin B-6 and pyridoxal-5 phosphate (PLP) (physiologically active coenzyme form of vitamin B-6). Urine will be analyzed for total vitamin B-6 and 4-pyridoxic acid (4-PA) (major excretory metabolite of vitamin B-6). The differences in total plasma vitamin B-6, PLP and urinary B-6 and 4-PA, before and after the vitamin load will serve as indices of absorption, phosphoxylation and degree of excretion, respectively. Dietary intake of vitamin B-6 will be determined from average of 3-day food intake records. The biochemical and dietary data will be analyzed by analysis of variance to determine differences among groups.